I think the conveniences are still tradeoffs though. A separate vehicle is handy for being able to slowly collect things to get rid of in one later trip, or to store something you just got until you're ready to put it somewhere else (I've currently got what remains of a 1/2 yard of sand sitting in mine). And being able to just dump something and drive away is quite nice (especially when you've put it into the trailer using equipment to begin with).

On the other hand, I've never experienced being able to just haul something without a little planning first, so I don't miss it.